Lead and cadmium are toxic elements, which are a natural part of earth crust. They are taken up from the soil and transferred upwards in the plant and animal food chain.
Cadmium is widely distributed throughout the natural environment with human activities having an important role in its dispersion into the biosphere. The natural sources of cadmium are volcanic eruptions and old granite rocks, which are an important geochemical source. Anthropogenic sources of cadmium are related mainly to mining, fertilizers and atmospheric deposition.
Leaded gasoline has been most important source of atmospheric lead. However, most countries have now prohibited the use of leaded gasoline. This action has greatly reduced emissions of lead into the atmosphere. Anthropogenic sources of lead other than traffic are typically fossil fuel combustion, non-ferrous metal production and iron and steel production.
Zinc and copper are important constituents in a number of different enzyme functions in man and animals. Zinc and copper reach the environment via industrial releases involving production and refining of metals.
In 1997 emissions of heavy metal particulates were only a third of their values in the early 1990s due to the installation of sulphur removal systems.
In this study lead, cadmium, copper and zinc levels in Finnish game animals (moose, hares) and farmed game animal (reindeer) were studied during twenty years period. About 500 moose were collected between 1980 and 1999 from south western, southern, central and south eastern Finland. About the same number of Mountain and European hare samples were collected during the period 1980 and 1993 from south western, southern, south eastern and northern Finland. About 300 reindeer were collected in 1990–1992 from southern, eastern, western and northern Lapland. After these initial projects, it was decided to collect moose and reindeer samples every year as part of national residue control program; fifteen moose and ten reindeer per year. In this residue control program, also cattle samples have been collected regularly; muscle, liver and kidney from 30 animals in every year.
The lead and cadmium levels in muscle tissue has decreased in all studied animals during the monitoring years being now near to the limit of quantification; 0.01 mg/kg w.w. for lead and 0.001 mg/kg w.w for cadmium. Also the lead levels in liver and kidney samples have decreased during the monitoring period but the moose cadmium levels have increased. The zinc levels had also increased in moose samples but there were no significant
correlation with increasing cadmium and zinc levels. The lead levels in liver and kidney in moose varied in 1999 from 0.04 to 0.07 mg/kg w.w. and 0.05-0.07 mg/kg w.w. The corresponding values for cadmium are 0.71-1.28 mg/kg w.w. and 4.95- 6.18 mg/kg w.w.
The cadmium and lead levels in Mountain hares are higher than in European hares and the kidney cadmium levels in Mountain hares are statistically significantly higher than the kidney cadmium levels in moose.
The lead levels in liver and kidney samples in both adult and calves of reindeer have been invariably below the recommended maximum level in the EU (0.5 mg/kg). However, the kidney cadmium level exceeds the maximum level (1.0 mg/kg) in almost all adult reindeer samples and also in some calves.
The meat of Finnish moose, reindeer and hares does not contain residues of cadmium and lead and therefore consumers can be assured that consumption of the meat is not a health risk. The consumption of the organs of the animals studied may represent a health risk for human.
However, the levels are far from the toxic levels to the animals themselves.